The increased popularity of such outdoor sports as hiking, bicycling and mountaineering has resulted in the proliferation of a variety of shelter structures which enable the participants in these sports to enjoy them for lengthy periods of time in locations which may be quite remote from conventional shelter. The ideal shelter structure for the aforementioned activities must be sufficiently lightweight and portable to be carried readily from one location to another as well as easy to assemble and disassemble and must be adaptable to a wide variety of environmental conditions. Once assembled, the ideal shelter structure must be stable enough to resist wind loads such as are particularly likely to be encountered at high mountain elevations and other environmental stresses. In addition, adequate ventilation of the shelter is essential, and the largest amount of floor space and head room possible in such a structure is highly desirable for the comfort of the shelter occupant or occupants. The ideal shelter will also be very lightweight and easily carried in a back-pack, yet will provide a large enough floor area to accommodate comfortably the occupants and their gear.
The shelter structures proposed by the prior art, while lightweight and portable, generally suffer from a number of disadvantages, the major of these being their lack of stability and their inability to shed wind loads and thus prevent the shelter structure from shifting its position. In addition, many prior art structures do not provide either optimum ventilation or interior space for the shelter occupants.
Prior art structures usually require anchoring stakes or external guy wires to stabilize them and secure them to the ground. The double walled structure disclosed by Moss in U.S. Pat. No. 4,236,543 is disclosed to hold its shape and maintain stability without staking or guy lines because the opposing side walls are held tense by resiliently flexible pole members held in a flexed condition by tunnels affixed to peripheral portions of the side walls. However, this arrangement, while more stable than many prior art structures, does not distribute stress evenly over the structure side walls and thus is not as effective in shedding wind loads and preventing shifting of the structure during high wind conditions without the attachment of external guy lines as is desirable. Further, the flat sidewall of the Moss tent yields an "A" frame profile which substantially reduces the interior volume, and the relationship between the weight and floor space area provided by the type of structure disclosed by Moss renders it heavier and smaller than desirable for many mountain climbers, backpackers and bicyclists.
The adequacy of ventilation is another problem which prior art shelter structures have not adequately addressed. Structures intended for use as shelter and protection from adverse weather must necessarily be weathertight so that the shelter occupants are, in fact, protected from the elements. However, while protecting the occupants, such a shelter must also deal effectively with condensation which forms on any surface whose temperature is below the dew point of the ambient air. Providing both adequate protection in untoward weather conditions and adequate ventilation is essential for the comfort and safety of the shelter occupants. However, the "chimney" type ventilation arrangement found in some prior art tent designs does not fully address these concerns. Prior art tent and shelter designs typically provide a double wall construction, wherein the exterior wall or fly is made from a waterproof material, for protection of the shelter occupant in bad weather. Such a shelter is disclosed in U.S. Pat. Nos. 3,790,096 to Nicolai; 4,165,757 to Marks; and 4,236,543 to Moss. This construction, however, does not eliminate the condensation which is likely to form inside the fly as a result of inadequate ventilation of the fly during bad weather. In addition, the separate fly structure may add significantly to the weight of shelter, which is a serious concern to many backpackers.
The prior art, therefore, has failed to provide a lightweight, portable, well-ventilated shelter structure having a sufficiently large amount of both floor space and head room for more than one occupant as well as an extremely stable aerodynamic configuration which is able to withstand adverse environmental conditions.